DIFFERENTIAL K-MUSCLE CELLS ISOLATED FROM THE PULMONARY ARTERIAL TREEOF THE RAT( CHANNEL DISTRIBUTION IN SMOOTH)

Intracellular photorelease of Ca2+ demonstrated the presence of Ca2+-a ctivated K+ channels in smooth muscle cells isolated from different lo cations of the rat pulmonary arterial tree. However, cell-free patch s tudies revealed marked differences in K+ channel distribution. In the main pulmonary artery the most frequently observed K+ channel was a si milar to 245pS conductance Ca2+- and ATP-activated (K-Ca,K-ATP) channe l. In small pulmonary arteries two K+ channel types predominated: the K-Ca,K-ATP channel and a similar to 185pS conductance K+ channel insen sitive to intracellular Ca2+, ATP and voltage. This difference in K+ c hannel distribution may highlight a more complex regulatory mechanism for controlling membrane potential in small pulmonary arteries,reflect ing their physiologically more important role in governing pulmonary v ascular reactivity. (C) 1995 Academic Press, Inc.